Thioxanthone carboxylic acids and derivatives

ABSTRACT

Compositions containing and methods employing, as the essential ingredient, thioxanthone carboxylic acid compounds which are useful in the treatment of allergic conditions. Methods for preparing these compounds and compositions are also disclosed. Thioxanthone-2-carboxylic acid and 7-methoxy-thioxanthone-2carboxylic acid are illustrated as representative of the class.

United States Patent Pfister et al. Sept. 9, 1975 [54] THIOXANTHONE CARBOXYLIC ACIDS 3,642,997 2/1972 Shen et al. 424/250 AND DERIVATIVES 3,706,768 12/1972 Bays 260/335 [75] Inventors: Jurg R. Pfister, Los Altos; Ian T. OTHER PUBLICATION Harrison; J n H Fried, both of Vasiliu, Rev. Chim., 1968, 19( 10), 561-565. P810 AltO, all Of Calif- Vasiliu (II), Rev. Chim., 1969, 20(9), 545546. [73] Assigneez syntax (USA) Inc palo Alto, Gialdi et al., Farmaco, Ed. Sci. 14, 830-844, (1959). C lif Burger, Medicinal Chemistry, (Interscience, 1960),

pp. 74-81. [22] Flled 1972 Conant, Chem. of Org. Cpds., (1934), p. 269. [21] Appl. No.: 308,569 Lowy, An Intro. to Org. Chem., (1945), pp. 213-215.

f U'S' Apphcatlon Data Primary Examiner-Henry R. Jiles [63] Continuation-impart of Ser. No. 273,290, July 19, Assistant c S. Jaisle 1972 Attorney, Agent, or Firm-Gerard A. Blaufarb; Walter '11 B. W 1k 52 us. Cl 260/328; 260/250 A; 260/250 R; H Dreger a er 260/251 R; 260/256.5 R; 260/294.8 B; 260/307 H; 260/307 R; 260/309; 260/310 R;

260/326.3; 424/250; 424/251; 424/263; [57] A BSTRACT 424/272; 424/273; 424/274; 424/275 Compositions containing and methods employing, as [51] Int. Cl C07d 65/18 the essential ingredient thioxamhone carboxylic acid [58] Field of Search 260/328, 250 A, 250 R compounds which are useful. in the treatment of aller- 260/251 R, 256.5 R, 294.8 B, 307 H, 307 R7 gic Conditions. Methods for preparing these com- 309, 310 R, 3263 pounds and compositions are also disclosed.

ThioXanthone-2-carboxylic acid and 7-methoxy- [56] References Cited thioxanthone-2-carboxylic acid are illustrated as rep- UNITED STATES PATENTS l/l963 Doebel ct al. 260/328 resentative of the class.

23 Claims, No Drawings THIOXANTHONE CARBOXYLIC ACIDS AND DERIVATIVES This is a continuation-in-part of application Ser. No. 273.290, filed July 19, 1972.

The present invention is directed to thioxanthone carboxylic acid compounds and to compositions containing and methods utilizing these compounds as the essential ingredient in the treatment of symptoms associated with allergic manifestations, for example, asthmatic conditions.

In a first aspect, the present invention relates to thioxanthone carboxylic acid compounds selected from those represented by the following formulas:

OOH

and the pharmaccutically acceptable, non-toxic esters, amides and salts thereof; wherein each m is the integer (l, l or 2, each R is lower alkyl: lower alkoxy; hydroxy and the conventional esters thereof; halo; mercapto; lower alkylthio; trifluoromethyl; or a group selected from those of the formulas:

in which R is hydrogen, lower alkyl. cycloalkyl. tet rahydrofuran-Z-yl. tetrahydropyran-Z-yl, tetrahydropyran-4-yl, 4-alkoxytetrahydropyran l-yl, or acyl containing up to 12 carbon atoms; R is hydrogen. lower alkyl. or cycloalkyl; R" is hydrogen, lower alkyl. cycloalkyl, phenyl, substituted phenyl (in which the substituent is halo, lower alkyl, lower alkoxy. lower alkylthio. trifluoromethyl, or cyano), or a monoc clic aromatic heterocyclic group having live or six total members. one or two of which are selected from nitrogen. oxygen, and sulfur; n is the integer l or 2. R is lower alkpl when n is l and R is lower alkyl, hydroxy. amino. monolowcr alkylamino, or dilowcr alkylamino when n is 2.

[ii a second aspect, the present invention is directed to a method useful for relieving symptoms associated with allergic manifestations such as are brought about by antigenantibody (allergic) reactions. In the relief of these symptoms, the method hereof serves to inhibit the effects of the allergic reaction when administered in an effective amount. While not intending to be bound by any theoretical mechanism of action, the method hereof is believed to operate by inhibiting the release and/or the action of toxic products, eg histamine, S-hydroxytryptamine, slow releasing substance (SRS-A). and others. which are produced as a result of a combination of specific antibody and antigen (allergic reaction). These properties make the subject compounds particularly useful in the treatment of various allergic conditions.

The compounds of the present invention also exhibit ll (Ol bronchopulmonary, e.g. bronchialdilating, activity and are therefore useful in the treatment of conditions in which such agents may be indicated, as for instance in the treatment of broncho constriction.

This aspect of the present invention thus relates to a method useful for inhibiting the effects of the allergic reaction and for the treatment of bronchopulmonary disorders which comprises administering an effective amount of a compound selected from those represented and defined by the above formulas; or a pharmaceutieally acceptable non-toxic composition incorporating said compound as an essential ingredient.

The present invention. in a third aspect, is directed to pharmaceutical compositions useful for inhibiting the effects ofthe allergic reaction and for the treatment of bronehopulmonary disorders comprising an effective amount of a compound selected from those represented and defined by the above formulas; in admixture with a pharmaccutically acceptable nontoxic carrier.

in the practice of the method of the present invcntion. an effective amount of a compound ofthc present imention or pharmaceutical compositions thereof, as defined abme. is administered via any of the usual and acceptable methods known in the art, either singly or in combination with another compound or compounds of the present invention or other pharmaceutical agents. such as antibiotics. hormonal agents, and so forth. These compounds or compositions can thus be administered orally, topically, parenterally. or by inhalation and in the form of either solid. liquid. or gaseous dosages including tablets, suspensions, and aerosols. as

discussed in more detail hereinafter. The administration can be conducted in single unit dosage form with continuous therapy or in single dose therapy ad libitum. In the preferred embodiments, the method of the present invention is practiced when relief of symptoms is specifically required, or, perhaps, imminent; however, the method hereof is also usefully practiced as continu ous or prophylactic treatment.

In view of the foregoing as well as in consideration of the degree or severity of the condition being treated, age of subject, and so forth, all of which factors being determinable by routine experimentation by one skilled in the art; the effective dosage in accordance herewith can vary over a wide range. Generally, an effective amount ranges from about 0.005 to about 100 mg. per kg. of body weight per day and preferably from about 0.01 to about I00 mg. per kg. of body weight per day. In alternate terms, an effective amount in accordance herewith generally ranges from about 0.5 to about 7,000 mg. per day per subject.

Useful pharmaceutical carriers for the preparation of the compositions hereof, can be solids, liquids, or gases. Thus, the compositions can take the form of tablets, pills, capsules, powders, sustained release formulations, solutions, suspensions, elixirs, aerosols, and the like. The carriers can be selected from the various oils including those of petroleum, animal, vegetable, or synthetic origin, for example, peanut oil, soybean oil, mineral oil, sesame oil, and the like. Water, saline, aqueous dextrose, and glycols are preferred liquid carriers, particularly for injectable solutions. Suitable pharmaceuti- 4 com 00R (R H hal COOR5 (R alo i v H cal excipients include starch, cellulose, talc, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, magnesium carbonate, magnesium stearate, sodium stearatc. glyceryl monostearate, sodium cloride, dried skim milk, glycerol, propylene glycol, water, ethanol. and the like. Suitable pharmaceutical carriers and their formulation are described in Remingtons Pharmaceutical Sciences by E. W. Martin. Such compositions will, in any event, contain an effective amount of the active compound together with a suitable amount of carrier so as to prepare the proper dosage form for proper administration to the host.

The compounds of the present invention demonstrate activity as inhibitors of the effects of the allergic reaction as measured by tests indicative of such activity involving passive cutaneous anaphylaxis as substantially described, for example, by J. Goose et al., Immunology, I6, 749 (1969).

The compounds of the present invention demonstrate bronchopulmonary activity as measured by tests indicative of such activity involving the isolated tracheal chain assay as substantially described, for example, by J. C. Castillo et al., Journal of Pharmacology and Experimental Therapeutics, Vol. 90, page 104 (1947) and the histamine aerosol bronchoconstriction assay as substantially described, for example, by O. H. Siegmund et al., Journal of Pharmacology and Iivperimental Therapeutics, Vol. 90, page 254 (1947).

Certain of the compounds of the present invention can be prepared in accordance with the following reaction sequence:

Seguence A 4 EJIORS cooR (R Sequence A Continued the products 9) is hydrogen, lower alkyl, lower alkoxy, hydroxy, halo, mercapto, lower alkylthio, trifluoromethyl or acyl; m is the integer 0, l, or 2; n is the integer l or 2; halo is bromo, chloro, fluoro, or iodo, preferably bromo; and each R is hydrogen or lower alkyl, preferably hydrogen or methyl.

With reference to the above reaction sequence, the o-mercaptobenzoic acid (1, R ==hydrogen) and phalobenzoic acid (2, R hydrogen) are condensed in the presence of copper powder with anhydrous potassium carbonate, optionally in organic liquid reaction medium, preferably an organic amide, such as dimethylacetamide, dimethylformamide N- methylpyrrolidone, tetramethylurea, and so forth, to prepare the corresponding diacid compound (7; m=o).

The reaction is preferably conducted in an inert organic reaction medium, such as those listed above, or suitable mixtures of one or more of such media. The reaction is further conducted at temperatures ranging from about 80 to about 220C, preferably from about 120 to 200C, and for a period of time sufficient to Complete the reaction, ranging from about 1 hour to about 4 hours.

The reaction consumes the reactants on the basis of one mole each of the reactants; however, the amounts of the reactants to be employed are not critical, some of the desired compound (7) product being obtained when employing any proportions thereof. In the preferred embodiments, the'reaction is conducted by reacting from about 1 to about 3 moles each of the respective starting compounds in the presence of 3 to 5 moles of potassium carbonate and catalytic amounts of the copper powder. The inert organic reaction medium, if employed, is used in solvent amountsv Similarly, the o-halobenzoic acid (3, R =h vdrogen) COOH and p-mercaptobenzoic acid (4, R hydrogen) are condensed, as described above, to give the product (7; m=o). In a similar manner, the mercaptobenzene compound (5) is condensed with the 4-halo-l,3- dicarboxybenzene (o), as described above, to give the diacid product (8; m=o).

Alternatively, the above-described eondensations are conducted with the corresponding esters of compounds 1), (2), (3), (4), and (6), Le. R =lower alkyl, to give the corresponding and respective diester (R"=lower alkyl) products (7) and (8). These condensations are conducted with the respective ester starting compounds in the presence of cuprous oxide optionally in organic liquid reaction medium, preferably an organic amide, such as dimethyl acetamide, dimethylformamide, N-methylpyrrolidone, tetramethylurea, and so forth.

The reaction is preferably conducted in an inert organic reaction medium, such as those listed above, or suitable mixtures ofone or more of such media. The reaction is further conducted at temperatures ranging from about 80 to about 220C, preferably from about l20 to 200C, and for a period of time sufficient to complete the reaction, ranging from about 2 hours to about 24 hours.

The reaction consumes the reactants on the basis of one mole each of respective reactant per half mole of cuprous oxide. However, the amounts of the reactants to be employed are not critical, some of the desired compound product being obtained when employing any proportions thereof. In the preferred embodiments. the reaction is conducted by reacting from about 1 to about 1.1 moles each of the respective reactant in the presence of from about 0.5 to about 0.6 moles of the cuprous oxide, The inert organic reaction medium, if employed, is used in solvent amounts.

Thereafter, the prepared ester compounds (7) and (8) are base hydrolyzed to give the corresponding diacid compounds (7) and (8) (R hydrogen; m o), obtained directly in the alternate procedure described above, with copper powder and potassium carbonate. The base hydrolysis conditions can be any employed conventionally in the art. Generally. the hydrolysis reaction is conducted using an alkali metal hydroxide at about 50 to about 90C and for a period of time sufficient to complete the reaction, ranging from about l minutes to about 60 minutes, preferably in the presence of inert organic reaction media, such as those normally employed in organic chemical reactions of this type, eg aqueous alkanol solutions. Although two moles of base are required per mole of compound (7) or (8), the amounts employed are not critical to produce the desired hydrolysis. Preferably from about 3 to about 5 moles of base are employed per mole of compound (7) 0r (8) and the reaction medium is used in solvent amounts.

The thus prepared diacid compounds (7) and (8) are then cyclized with phosphoryl chloride, thionyl chloride, sulfuric acid, hydrogen fluoride, or, preferably polyphosphoric acid (PPA), to give the corresponding substituted thioxanthone-Z-carboxylic acid compound (9; m=o). The reaction is preferably, but optionally, conducted in an inert organic reaction medium includ ing those usually employed in organic chemical reac tions such as dimethylsulfoxide sulfolane, benzene, toluene, and so forth. The reaction is further conducted at temperatures ranging from about 60 to about l80C and for a period of time sufficient to complete the reaction ranging from about minutes to about 90 minutes.

Although the reaction consumes the reactants on the basis of one mole of starting compound (7) or (8) per mole of cyclizing reagent, the reaction can be performed using any proportion of reactants. In the preferred embodiments, however. the reaction is conducted using from about to about 50 moles of the cyclizing reagent per mole of starting compound.

Alternative to the above described method, the (lower alkoxy) thioxanthone2-carboxylic acid compounds can also be prepared by following the aboveindicated sequence which is practiced using a hydroxy or methoxy substituted (R starting compound, (I).

(3). or (5), cleaving the mcthoxy substituted product (9) with hydrobromic or hydroiodic acid and acetic acid. followed by treatment the thu. prepared bydroxy compound (9) with a lower alkyl halide in the presence of base followed by base treatment.

The conventional esters of the thus prepared hydroxy (R compounds (9) are conventionally prepared by means known to those skilled in the art, for example, by treatment of the hydroxy compound with lower alkanoyl chloride or carboxylic anhydride in pyridine.

Compounds (7) and (8) wherein m=o, prepared as described above, can be oxidized with a peracid, such as peracetic acid, m-chloroperbenzoic acid, pnitroperbenzoic acid, perphthalic acid, and so forth, to give the corresponding compounds wherein m is l or 2 and, accordingly, the products (9) wherein m is l or 2. The oxidation is preferably conducted in liquid reac tion media, such as a chlorinated hydrocarbon, e.g. chloroform, methylene chloride, and carbon tetrachloride. The reaction is conducted at temperatures ranging from about 0 to about C, preferably from 20 to about 30 and for a period of time sufficient to complete the reaction, ranging from about 1 hour to about 6 hours. When conducted at about 0C with about l mole of peracid, the lO-oxo (7, 8; rn-l) compounds are prepared; when conducted at about room temperature or more with about 2 moles of peracid. the 10,10- dioxo (7,8; m=2) compounds are prepared. The thus prepared oxo compounds are thereafter treated as hereinafter described to prepare the substituted thioxanthone compounds hereof in the lO-oxo and 10,10- dioxo series.

Alternatively, the compounds (9), wherein m=o, prepared as described above, can be oxidized to give the corresponding products (9), wherein m=l or 2. When the oxidation is conducted with iodosobenzene in acetic acid, the products (9), wherein m=l, are'prepared; when the oxidation is conducted with hydrogen peroxide in acetic acid, the products (9), wherein m=2, are prepared.

Certain of the compounds of the present invention can be prepared as follows:

Seguence B Sequence B-Continued 0 (DH I R O OH OCH 2| l R wherein R" is R exclusive of hydrogen and R is R exclusive of hydrogen, and n is as above defined.

With reference to the above reaction sequence. the C-5, C-6, G7, or C-5,7 acyl substituted thioxanthone- Z-carboxylate 10) (prepared as described above. 5+6 8 9) can be hydrolyzed, as described above. to give the acylthioxanthone-2-carboxylic acid compounds l5 Compounds 10) can also be reduced. such by the known method using sodium borohydride, to give the corresponding (secondary hydroxyalkyl thioxanthone-Z-carboxylate esters (13) which can be hydrolyzed to the acid products ([4).

Compounds 10) can also be treated with alkyl or cycloalkyl (Le. R Grignard reagent, under known Grignard reaction conditions, to give the correspond- 3 ing (tertiary hydroxyalkyl )-thioxanthone-2-carboxylate esters (l l which can be hydrolyzed to the acid products l2).

Certain of the compounds of the present invention can be prepared in accordance with the following reac- 40 tlon sequence:

Seguence C r 0 OOH 00115 n a i wherein each of R and n is as defined above; R is hydrogen or lower alkyl; and each of R R, R", R'", and R" is lower alkyl.

With reference to the above reaction sequence. a C-5, C-7, or C-5,7 alkoxy substituted compound 16; R"=hydrogen) (prepared as described in Sequence A (5+6 8 9) is converted to the respective hydroxy compounds 16; R hydrogen) by treatment with hydrobromic or hydroiodic acid and acetic acid. This reaction is conducted at a temperature of from about 100 to about 160C. The thus prepared 5- and 7-hydroxy acid compounds are then csterified (R to give compounds (17). This reaction is conducted with the desired lower alkyl iodide in the presence of lithium carbonate, at room temperature or with the desired lower alkanol in the presence ofa trace of sulfuric acid at reflux.

The hydroxy acid esters 17) are then treated with a dialkylthiocarbamoyl chloride, such as dimethylthiocarbamoyl chloride, in the presence of base, such as an alkali metal hydride, and in organic liquid reaction media, preferably an organic amide. such as those listed above, to afford the products 18 The reaction is conducted at temperatures ranging from about to about 100C, preferably from 60 to about 80C and for a period of time sufficient to complete the reaction. ranging from about 1 hour to about 6 hours. In the preferred embodiments, the reaction is conducted by reaction of from about 1.1 to about 1.5 moles of dialkylthiocarbamoyl chloride per mole of compound l7 The product compounds 18) are then rearranged by reaction at a temperature of from about 200 to about 250C, preferably from about 220 to about 230C, and for a period of time ranging from about 1 hour to about 8 hours and in the presence of organic medium, such as sulfolane, nitrobenzene. triethylencglycol, and so forth, which is preferably employed in solvent amounts, to give compound l9).

Compounds (19) are then converted to the corresponding mercapto acid compounds (20) by base bydrolysis, as described above. The lower alkylthio ether, ester compounds (21 are then prepared, as described above, or by reacting compounds (20) with a lower alkyl halide in the presence of base, such as potassium carbonate and organic liquid reaction media, such as those described above. The reaction is conducted at a temperature ranging from about 20 to about 90C, preferably from 50 to about 80C and for a period of time sufficient to complete the reaction, ranging from about 2 hours to about 16 hours.

Hydrolysis of the ester (21), as described above. affords the (lower alkylthio)acid compounds (22).

Compound (21 can be oxidized with a peracid, such as peracetic acid, mchloroperbenzoic acid, pnitroperbenzoic acid, perphthalie acid, and so forth, to give compounds (23) and (24) which can be hydrolyzed, as above described, to give the corresponding compounds (25) and (26), respectively. The oxidation is preferably conducted in liquid reaction media, such as a chlorinated hydrocarbon, e.g. chloroform, methy lene chloride. and carbon tetrachloride. The reaction is conducted at temperatures ranging from about 0 to about 60C, preferably at about 0C for preparing the sulfinyl compounds and at about room temperature for preparing the sulfonyl compounds and for a period of time sufficient to complete the reaction, ranging from about 1 hour to about 6 hours. In the preferred embodiments, the reaction is conducted by reaction of from about 1 to about 2.2 moles of peracid.

In said oxidation steps, a mixture of products (23) and (24) may be obtained which mixture can be conventionally separated, such via chromatography, if desired, to isolate the oxidized products.

The above oxidation steps can also be practiced on starting compounds (22) to give respective products (25) or (26) without the need of a second hydrolysis step.

Alternatively, compounds (20) can be treated with excess chlorine under acidic conditions to afford compounds (27). This reaction is conducted employing a pH of about 1 by use of hydrochloric acid, optionally in acetic acid solution. The reaction is further conducted at temperatures ranging from about 20 to about 100C, preferably from to about C and for a period of time sufficient to complete the reaction, ranging from about 2 hours to about 12 hours.

Compound (27) is then reacted with a base, such as alkali metal hydroxide under aqueous conditions and at a temperature ranging from about 20 to about 100C, preferably from to about C and for a period of from about 1 hour to about 2 hours to give the sulfosubstituted acid compounds (28).

Compounds (27) can be treated with ammonia, monolower alkylamine, or dilower alkylamine to give the sulfamoyl, monolower alkylsulfamoyl, and dilower alkylsulfamoyl acid compounds (29). This reaction is conducted at temperatures ranging from about 0 to about 80C, preferably from 20 to about 30C, and for a period of time sufficient to complete the reaction, ranging from about 1 hour to about 8 hours. In the preferred embodiments, the reaction is conducted by reaction of from about 10 to about 20 moles of amine per mole of compound (27). This reaction is further conducted in organic reaction media, such as those de scribed above, preferably tetrahydrofuran, dioxane, di methylsulfoxide, and so forth.

The C-5, C-7, and C-5,7 chlorosulfonylthioxanthone- Z-carboxylic acid compounds (27) are novel intermediates useful as described above.

Certain of the compounds of the present invention can be prepared in accordance with the following reaction sequence:

Sequence D OOH Sequence D -Cntinued OOH wherein each of R and R is as above defined.

With reference to the above reaction sequence, paramercaptobenzoic acid (4) is condensed with the 2,4- dichlorobenzoic acid as described above in Sequence A, with copper powder and anhydrous potassium carbonate to give compound (31).

The thus-prepared diacid compound (3 l is then cyclized, as described above in Sequence A. with phosphoryl chloride. thionyl chloride, sulfuric acid, hydrogen fluoride, or, preferably. polyphosphoric acid (PPA to give the corresponding 6- ehlorothioxanthone-2-carboxylic acid compound (32 The 6-chlorothioxanthonc-Z-carbovylic acid (33) is then treated with excess alkali metal lower alkoxide, e.g. sodium methoxide, to give compound (34) or with excess alkali metal thiolowcralkoxide to give compounds (33). The reaction is preferably conducted in OOH OOH

OOH

polar organic solvent at temperatures of from about to about C.

The o-methoxythioxanthone-Z-carboxylic acid compound (34) thus prepared is converted to the respective o-hydroxy compound by treatment with hydrobromic or hydroiodic acid and acetic acid. This reaction is conducted at a temperature of from about 100 to about C followed by esterification (R") to give compounds (35).

The alkylthio or hydroxy acid esters (33) and (35) are then treated, as described above in Sequence C (17 18 et seq). to give the corresponding 6- substituted products hereof.

Certain of the compounds of the present invention can be prepared in accordance with the following reaction sequences:

Sequence E COOR Sequence F Continued 0 15 OOH OOH S a i 14 SR14 SR wherein R is as above defined; each of R and R is lower alkyl, lower alkoxy hydroxy, halo, or trifluoromethyl; and each of R and R is lower alkyl.

With reference to the above reaction sequences E and F, the 5- or 7-substitutedcompounds (39) and corresponding compounds (46) are prepared as described above in Sequence A. Thereafter, the respechal 5 COOR COOH OOH

tive products are oxidized to the sulfinyl and sulfonyl compounds either directly or through the acid esters, as described above.

Certain of the compounds of the present invention can be prepared in accordance with the following reaction sequence:

Seguence G COOR Sequence G C0ntinued fl Cl-fi OOH 9 o. OOH

o 0 (R n-isg OOH wherein each of halo, R and R is as defined above and R is lower alkyl, lower alkoxy, halo. hydroxy, mercapto, lower alkylthio, or trifluoromcthyl.

With reference to the above reaction sequence, the 5- or 7-suhstitutedcompounds (53) are prepared as described above in Sequence A. Thereafter, the 5- or 7-chlorosullbn \'l compounds (54) and (55) are preo OOH OOH coon o R16 OOH o OOH 16 o R OOH o=s =o pared by treating (53) with chlorosulfonic acid and these are converted to the sullfo compounds (56) and (57) or the sulfamoyl compounds (58) and (59), such as described above.

Certain of the compounds of the present invention can be prepared in accordance with the following reaction sequence:

Sequence H OOH wherein each of halo. R, R'" and R is as above defined.

With respect to the above reaction sequence. compound (53) is prepared as described in Sequence (it 'l'hereafter. the 9-oxo group is reduced. such as with potassium hydroxide in hydrazine, Zinc and potassium hydroxide in ethanol. and the like. to prepare the corresponding (-5 or 7 substituted xanthene-Z-carboxylic acid (60). This compound is esterilied (R). as described above. and the ester (61 then'acylated with a lower alkanoyl chloride in the presence olaluminum chloride to give the corresponding 5 or 7-lowcr alkanoyl compounds (62) and (63 l.

OOH

The compounds of formula (62 and 63) are oxidized with manganese dioxide to prepare the corresponding 5- or 7-( l-acyloxylower alkyl) Xanthtine-lcarboxylic acid esters (64 and 65) which. when hydrolyzed under base conditions. gives the corresponding thioxanthone- Z-carhoxylic acids (66 and 67 'lhe esters (62) and (63) can be reduced or treated with (irignard reagent. followed by oxidation at (-9 and hydrolysis to gi e the corresponding secondary and tertiary hydroxy alkyl thioxanthone-lcarboxylic acids.

'lhe carboxylic esters of the secondary and tertiary h droyy alkyl substituted compounds (i.e. R=carboxylic acyl) are prepared as described above or by secondary and tertiary alcohol esterification methods known per se. One such method involves treating the products represented by Formula (14) with a carboxylic acid chloride or carboxylic acid anhydride in the presence of a base, preferably pyridine, at temperatues ranging from about 60 to 90C and for a period of time ranging from about 1 to about 2 hours to give the corresponding secondary acyloxy alkyl substituted thioxanthone- 2-carboxylic acid compound. Likewise, by treating the products of Formula 12) with a carboxylic acid chloride and dimethylaniline in tetrahydrofuran or with a mixed carboxylic acid, p toluenesulfonic acid anhydride, the corresponding tertiary acyloxy alkyl substituted thioxanthone-2-carboxylic acid compounds are prepared. See Harrison and Harrison, Compendium of Organic S \'IlI/l[i( Methods, Wiley-Interscience, New York (1971), 281, and 2 and the references cited thereon.

The alkyl and cycloalkyl ethers of the secondary hydroxyalkyl series (R=alkyl, cycloalkyl) are prepared by treatment of the thioxanthone acid ester with the appropriate alkyl or cycloalkyl halide and sodium hydride in, eg. dimethylformamide, followed by hydrolysis, as described above. The etherification reaction is conducted at from about 50 to about 80C and for from about 1 to about 5 hours. In the tertiary alcohol series, the alkyl and cycloalkyl cthcrs are prepared by treating the precursor acyl compound, cg. 7-(acetyl)- thioxanthone-Zcarboxylic acid ester, under Grignard conditions, as described above, but in the presence of appropriate alkyl or cycloalkyl iodide or bromide and hexamcthylphosphoramidc to concomitantly afford the alkyl or cycloalkyl ether of the tertiary alcohol, followed by hydrolysis as described above. See Harrison and Harrison. Compendium ql'Oljg unit' .S'ynrhetic Met/zuz/x, Wiley-Intersciencc, New York (l971), 323 and the references cited thereon.

The t-butoxy cthers are prepared by treating the alcohol with isobutcne in the presence of boron trifluoride and phosphoric acid in, c.g. methylene chloride, at temperatures of from about 10 to about C and for from 10 to about 24 hours, or more, followed by hydrolysis of the acid ester group, as described above.

The tetrahydrofuran-2yloxy and tetrahydropyran-2- yloxy ethers in the secondary and tertiary alcohol series are prepared by treatment with dihydrofuran or dihydropyran in the presence ofp-toluenesulfonic acid and organic reaction medium, e.g. benzene, at about room temperature up to reflux, for from about 2 to about 5 days, followed by hydrolysis of the acid ester, as dc scribed above.

The 4-alkoxytctrahydropyran-4-yloxy ethcrs in the secondary and tertiary alcohol series are prepared by treatment ofthc alcohol with 4-111koxy-S.6-dihydro-2H- pyran, as described above for the preparation of the furanyl and pyranyl ethers, followed by acid ester hydrolysis. Treatment of the l-alktixytetrahydropyran-4- yloxy ether with aluminum chloride and lithium aluminum hydride in organic reaction medium affords the corresponding tctrahydropyran-4-yloxy cthcrs which are oxidized to give the corresponding ethers in the thi- ()Kllltlhtlllt, acid series. The latter can be directly prepared by treating the alcohol with 4-brtnnotctrahydropyran and base. See Harrison and Harrison, (om m1- tlimn o/Upqruih .S'ynlln'li'r' s'l Iz'l/Im/X, Wiley-lnterscience, New York 1971 l2) and the references cited thereon.

tion are known and can be prepared by processes known per se. 'lhus, the 1,3-dicarbo(lower)alkoxy-4- halobenzene starting compounds are conveniently prepared by oxidizing 1,3-dimethyl-4-halobenzene (4- halo-m-xylene) with potassium permanganate, as described above, followed by conventional esterification. The o,p-(diloweralkylthio)thiophenol compounds are conveniently prepared by chlorosulfonation of the cor responding m-dialkylthiobenzenes followed by reduction of the chlorosulfonyl group with zinc and sulfuric acid.

The o,p-dialkoxythiophenol starting compounds are prepared by chlorosulfonation of the corresponding mdialkoxybenzenes followed by reduction of the sulfonyl group with zinc and sulfuric acid.

The acid esters of the thioxanthone-2-carboxylic acids hereof are prepared upon treatment of the acid with ethereal diazoalkane, such as diazomethane and diazoethane, or with the desired lower alkyl iodide in the presence of lithium carbonate at room temperature or with the desired lower alkanol in the presence of a trace of sulfuric acid at reflux. The glycerol esters are prepared by treating the acid with thionyl chloride followed by treatment with a suitably protected ethylene glycol or propylene glycol (cg. solketal) in pyridine, and hydrolyzing the protecting group of the ester thus formed with dilute acid.

The amides of the thioxanthone-Z-carboxylic acids hereof are prepared by treatment of the acids with thionyl chloride followed by treatment with anhydrous ammonia, alkylamine, dialkylamine, dialkylaminoalkylamine, alkoxyalkylamine, or phenethylamine.

The salts of the thioxanthone-2-carboxylie acids hereof are prepared by treating the corresponding acids with pharmaceutically acceptable base. Representative salts derived from such pharmaceutieally acceptable bases are sodium, potassium, lithium, ammonium, calcium, magnesium, ferrous, ferric, zinc, manganous, aluminum, manganic, the salts of trimethylamine, triethylamine, tripropylamine, B-(dimcthylamino)ethanol, triethanolamine, Bldiethylamino)ethanol, arginine, lysine, histidine, N-

ethylpiperidine, hydrabamine, choline, betaine, ethyl enediamine, glucosamine, methyl glucamine, theobromine, purines, piperazine, piperidine, polyamine resins, caffeine, procaine, or the like. The reaction is conducted in an aqueous solution, alone or in combination with an inert, water miscible organic solvent, at a temperature of from about 0C to about C, preferably at room temperature. Typical inert, water miscible organic solvents include methanol, ethanol, isopropanol, butanol, acetone, dioxanc, or tctrahydrofuran. When divalent metal salts are prepared, such as the calcium saltsor magnesium salts of the acids, the free acid starting material is treated with about one-half molar equivalent of pharmaceutically acceptable base. When the aluminum salts of the acids are prepared, about onethird molar equivalent of the pharmaccutically acceptable base are employed.

In the preferred embodiment of the present invention, the calcium salts and magnesium salts olthc acids are prepared by treating the corresponding sodium or potassium salts of the acids with at least one-half molar equivalent ofcalcium chloride or magnesium chloride, respectively. in an aqueous solution, alone or in combination with an inert water miscible organic solvent, at a temperature of from about 20 to about 100C In the preferred embodiment of the present invention, the aluminum salts of the acids are prepared by treating the acids with at least one-third molar equivalent of an aluminum alkoxide, such as aluminum triethoxide, aluminum tripropoxide and the like. in a hydrocarbon solvent, such as benzene, xylene, cyelohcxane, and the like. at a temperature of from about 20 to about 1 15C.

In the present specification and claims, by the term lower alkyl is intended a lower alkyl group contain ing one to five carbon atoms including straight and branched chain groups and cyclic alkyl groups, for example, methyl, ethyl. n-propyl, isopropyl, n-butyl, isobutyl. sec-butyl, t-butyl, n-pentyl, isopentyl, sec-pentyl. and t-pentyl, cyclopropyl, cyclobutyl, and cyclopentyl. By the term lower alkoxy is intended the group lower alkyl wherein lower alkyl is as defined above. By the term lower alkyl thio is intended the group S-lower alkyl wherein lower alkyl" is as defined above. The term substituted phenyl includes psubstituted phenyl. The term monocyclic aromatic hete1oeyclic group" includes pyridyl, pyridazinyl, pyrimidinyl. pyrazinyl, pyrazolyl, imidazolyl, furanyl, thienyl, pyrrolyl, isoxazolyl, and oxazolyl.

The following examples illustrate the method by which the present invention can be practiced.

EXAMPLE 1 A mixture of grams of 4-bromobenzoic acid. 7.5 g. of omereaptoben2oic acid, 0.1 g. of copper powder and 8 g. of anhydrous potassium carbonate in 100 ml. of dimethylformamide is heated to 155C and maintained thereat with stirring and under a nitrogen atmosphere. After monitoring via tlc indicates the reaction is substantially complete, the reaction mixture is diluted with water, treated with charcoal, filtered and the clear filtrate acidified. The precipitate is isolated by suction filtration. washed neutral and dried to give 4- (2-carboxyphenylthio)-benzoic acid.

5.2 g. of 4-(2-carboxyphenylthio)-benzoic acid in 40 ml. of concentrated sulfuric acid is stirred at 25C for 8 hours. After this time, the reaction mixture is poured into 200 ml. of ice water and the resultant mixture is heated on a steam bath for minutes. The mixture is cooled and filtered with the precipitate being washed with water and then recrystallized from acetic acid to give thioxanthone-Z-carboxylic acid.

EXAMPLE 2 A mixture of 7.5 grams of 4-mercaptobenzoic acid, H) g. of o-bromobenzoic acid, 0.1 g. of copper powder and 8 g. of anhydrous potassium carbonate in 100 ml. of dimethylformamide is heated to 155C and maintained thercat with stirring and under a nitrogen atmosphere. After monitoring via tlc indicates the reaction is substantially complete, the reaction mixture is diluted with water, treated with charcoal, filtered and the clear filtrate acidified. The precipitate is isolated by suction filtration, washed neutral and dried to give 4- (2-carboxyphenylthio)-benzoic acid.

5.2 g. of 4-(2-carboxyphenylthio)-benzoic acid in 40 ml. of concentrated sulfuric acid is stirred at C for 8 hours. After this time, the reaction mixture is poured into 200 ml. of ice water and the resultant mixture is heated on a steam bath for 15 minutes. The mixture is cooled and filtered with the precipitate being washed with water and then recrystallized from acetic acid to give thioxanthone-Z-carboxylic acid.

EXAMPLE 3 A mixture of 4.9 grams of 1,3-dicarboxy-4- bromobenzene, 2.4 g. of thiophenol, 0.5 g. of copper powder and 6.5 g. ofanhydrous potassium carbonate in 5() ml. of dimethylformamide is heated to 150C and maintained thercat with stirring and under a nitrogen atmosphere. After monitoring via tlc indicates the reaction is substantially complete, the reaction mixture is diluted with water, treated with charcoal, filtered and the clear filtrate acidified. The precipitate is isolated by suction filtration. washed neutral and dried to give 1 ,3- dicarboxy-4-phenylthiobenzene.

3.9 grams of l,3-dicarboxy-4-phenylthiobenzene in 35 ml. of concentrated sulfuric acid is stirred at 25 C for 10 hours. After this time, the reaction mixture is poured into 200 ml. of ice water and the resultant mixture is heated on a steam bath for 15 minutes. The mixture is cooled and filtered with the precipitate being washed with water and then recrystallized from acetic acid to give thioxanthone-2-carboxylic acid.

The second step eyclization reaction of each of Examples l to 3 can also be conducted via the following representative procedure:

A mixture of l.94 g. of 4-(2-carboxyphenylthio)- benzoic acid, 40 ml. of sulfolane and 30 ml. of polyphosphoric acid is stirred at C for 30 minutes. The resultant mixture is then diluted with water and the diluted mixture filtered. The precipitate is washed neutral, and then dissolved and heated in ethanol containing charcoal. The resultant mixture is then filtered, and the ethanol is partially evaporated. Water is added until crystallization starts. Filtration gives the solid product thioxanthone-Z-carboxylic acid which can be recrystallized from ethanol.

EXAMPLE 4 The procedures of Examples 1, 2 and 3 are repeated using the appropriate substituted o-mercaptobenzoic acid (Paragraph 1 of Example 1 o-bromobenzoic acid (Paragraph 1 of Example 2), and thiophenol (Paragraph 1 of Example 3) to furnish the following substituted thioxanthone-2-carboxylic acid products: 7-(methyl)-thioxanthone-Z-carboxylic acid,

7-( ethyl )-thioxanthone-2-carboxylic acid, 7-(n-propyl )-thioxanthone-2-carboxylic acid, 7-(isopropyl)-thioxanthone-2-carboxylic acid, 7-(n-butyl )-thioxanthone-2-carboxylic acid, 7-(isobutyl)-thioxanthone-2-carboxylic acid,

7-( sec-butyl )-thioxanthone2-carboxylic acid,

7-( t-butyl )-thioxanthone-2-earboxylic acid, 7-(pentyl )-thioxanthone-Z-carboxylic acid, 7-(cyclopropyl)-thioxanthone-2-carboxylic acid, 7-(cycl0butyl )-thioxanthone-2-carboxylic acid,

7-( cyclopentyl )-thioxanthone-2-carboxylic acid, 7-(methoxy )-thioxanthone-2-carboxylie acid, 7-(ethoxy)thioxanthone-2-carboxylic acid.

7-( n-propoxy)-thioxanthone-2-carboxylic acid 7-(isopropoxy)-thioxanthone2-carboxylic acid,

7-( n-butoxy )-thioxanthone-2-carboxylic acid, 7-(isobutoxy)-thioxanthone-Z-carboxylic acid, 7-(sec-butoxy)-thioxanthone-2-carboxylie acid,

7-( t-butoxy )-thioxanthone-2-carboxylie acid, 7-(pentoxy)-thioxanthone-2-earboxylic acid,

7-( cyclopropoxy )-thioxanthone-2-earboxylic acid, 7-(cyclobutoxy)-thioxanthone-2-carboxylic acid,

7-( cyclopentoxy )-thioxanthone-2-carboxylic acid. 7-( hydroxy)-thioxanthone-Z-earboxylic acid,

7-( mercapto )-thioxanthone-2-carboxylic acid, 7-(methylthio)-thioxanthone-2-earboxylie acid. 7-(ethylthio)-thioxanthone-2-carboxylic acid,

7-( n-propylthio )-thioxanthone-2-carboxylie acid,

7-( isopropylthio)-thioxanthone-Z-carboxylic acid, 7-( n-butylthio)-thioxanthone-2-carboxylic acid.

7-( isobutylthio)-thioxanthone-Z-carboxylic acid, 7-(sec-butylthio)-thioxanthone-2carboxylic acid. 7-(t-butylthio )-thioxanthone-2-carboxylic acid.

7-(pentylthio)-thioxanthone-2-carboxylic acid, 7-(cyclopropylthio)-thioxanthone-2carboxylic acid, 7-( cyclobutylthio)-thioxanthone-2-carboxylic acid, 7-(cyclopentylthio)-thioxanthone-Z-carboxylic acid, '7-(trifluoromethyl)-thi0xanthone-2-carboxylic acid. 7-(acetyl )-thixanthone-2-carboxylic acid, 7( propionyl )-thioxanthonc-2-carboxylic acid, 7-(n-butyryl )-thioxanthone-2-carboxylic acid, 7-( isobutyryl )-thioxanthone-2-carboxylic acid, 7-( n-pentanoyl )-thioxanthone-Z-carboxylic acid, 7-(is0pentanoyl)-thioxanthone-2-carboxylic acid, 7-(sec-pentanoyl)-thioxanthone-2-carboxylic acid, 7-(t-pentanoyl)-thioxanthone-2-carboxylic acid, 7-(n-hexanoyl)-thioxanthone-2carboxylic acid, 7-( n-heptanoyl)-thioxanthone-2-carboxylic acid, 7( noctanoyl )-thioxanthone-Z-carboxylic acid, 7-(n-nonanoyl)-thioxanth0ne-2-carboxylic acid, 7-( cyclopropylcarbonyl )-thioxanthone-Z-carboxylic acid, 7-( cyclobutylcarbonyl )-thioxanthone-2-carboxylic acid, 7-( cyclopentylcarbonyl )-thioxanthone-Z-carboxylic acid, 7-( cyclohexylcarbonyl )-thioxanthone-Z-carboxylic acid, 7-( formyl )-thioxanthone l-carboxylic acid, 7-( chloro)-thioxanthone-Z-carboxylic acid, 7-( fluoro )-thioxanthone-Z-carboxylie acid, 7-( bromo )-thioxanthone-Z-carboxylic acid, 7-( benzoyl )-thioxanthoneQ-carboxylic acid, 7-( p-chlorobenzoyl )-thioxanthone-Z-carboxylic acid, 7-( p-methylbenzoyl )-thioxanthone-Z-carboxylic acid, 7( p-mcthoxybenzoyl )-thioxanthone-2-carboxylic acid, 7-( p-thiomethoxybcnzoyl )-thioxanthone-2- carboxylic acid, 7-( furoyl )-thioXanthone-Zcarboxylie acid, 7-( pyrroyl )-thioxanthone-Z-carboxylic acid, 7-( thcnoyl )-thioxanthone-Z-carboxylic acid, 7-(pyridylcarbonyl)-thioxanthone-2carboxylic acid, 7-( imidazolylcarbonyl )-thioxanthone-Z-carboxylic acid, and 7-( oxazolylcarbonyl )-thioxanthone-2-carboxylic acid, and the corresponding 70 compounds in the C-5 substituted series, i.e. 5-(methyl)- thioxanthonc2-carboxylic acid, 5-( ethyl thioxanthone-Z-carboxylic acid, 5-(isopropoxy)- thioxanthone-Z-carboxylic acid, and so forth, and the corresponding 70 compounds in the C-6 substituted series, i.c. 6-(methyl)-thioxanthone-2- carboxylic acid, (Methyl)-thioxanthone2- carboxylic acid, 6-(isopropoxy)thioxanthone2- carboxylic acid, and so forth, and the corresponding 70 compounds in the (-5.7 disubstitutcd series, i.c. 5,7-di(methyl )-thioxanthone-2-carboxylic acid, 5.7-di(ethyl)-thi()xanthone-2-carboxylic acid. 5,7 (diisopropoxy)-thioxanthone-Z-carboxylic acid, and so forth.

EXAMPLE 5 A mixture of 4.188 grams of 1,3-dicarbomethoxy-4- bromobenzcne. 2.85 g. of p-(methoxy)-thiophenol. 1.32 g. of cuprous oxide in ml. of dimethylacetamidc is heated to 160C and maintained thercat with stirring and under a nitrogen atmosphere. After monitoring via tlc indicates the reaction is substantially complete. the reaction mixture is diluted with water and extracted with dicthylether:methylene chloride (3:1

The extracts are chromatographed on 150 g. of alumina and the uniform fractions combined to give 1,3- dicarbomethoxy-4-( p-( methoXy)-thiophenyloxy) benzene.

1 ,3-Dicarbometh0xy-4-( p-( methoxy)-thiophenyloxy)-benzene (3 g.) is combined with ml. of 5% potassium hydroxide in methanol. The resultant mixture is refluxed for one hour after which time it is acidified, cooled and filtered, to give 1,3-dicarboxy-4-(p- (methoxy )-thiophenyloxy )-benzene.

A mixture of 1.94 g. of 1,3-dicarboxy-4(p- (methoxy)-thiophenyloxy-benzene, 40 ml. of sulfolane and 30 ml. of polyphosphoric acid is stirred at C for 30 minutes. The resultant mixture is then diluted with water and the diluted mixture filtered. The precipitate is washed neutral, and then dissolved and heated in ethanol containing charcoal. The resultant mixture is then filtered, and the ethanol is partially evaporated. Water is added until crystallization starts. Filtration gives the solid product 7-(methoxy)-thioxanthone-2- carboxylic acid which can be recrystallized from etha' nol.

The foregoing procedure can be practiced using an alternative l,3dicarbolow eralkoxy-4-halo starting compound, such as 1,3-dica'rbomethoxy-4-chloro- (or iodo) benzene, l,3-dicarboethoXy-4-fluoro-benzene, l,3-dicarboethoxy4-bromobenzene, and the like, with similar results.

Likewise, the foregoing procedure can be practiced using the corresponding esters of the starting compounds of Examples 1 and 2, i.c. methyl 4- bromobenzoate and methyl o-mercaptobenzoate (Example 1) and methyl 4-mercaptobenzoate and methyl o-bromobenzoate (Example 2) to similarly prepare thioxanthone-Z-carboxylic acid.

Likewise prepared in accordance with the foregoing arc the other compounds listed in Example 4 above.

EXAMPLE 5A 4-(Z-Carboxyphenylthio)-benzoic acid (820 mg.) in 30 ml. of methylene chloride is cooled to 0C (ice). m- Chloropcrbenzoic acid (610 mg.) is then added and the mixture is stirred at 0C for 75 minutes. The reaction mixture is then filtered through alumina and washed with methylene chloride to give S-oxo-4-(2- carboxyphenylthio)benzoic acid. Similarly, S,S-dioxo- 4-(2-carboxyphenylthio)-benzoic acid is prepared using the excess peracid at 40C for 6 hours.

The thus prepared compounds are cyclized, as described in Examples 1 to 3, to give 10- oxothioxanthone-2-carboxylic acid and 10,10- dioxothioxanthone-2-carboxylic acid, respectively.

In like manner, l,3-dicarboxy-4-phenylthiobenzene can be so oxidized and the 0x0 products cyclized to give the l()-oxoand 10,10-dioxothioxanthone-2- carboxylic acid products.

Thus prepared, e.g. are the l()-oxo and 10,10-dioxo compounds otherwise corresponding to the products of Example 4, i.c.

7-methyll (J-oxothioxanthone- Z-carboxylic acid.

7meth vll (l, l (l-dioxothioxanthone-Z-carboxylic acid,

7-ethyll (l-oxothioxanthone-2-carboxylic acid.

7-ethyl-10,1(l-dioxothioxanthone-Z-carboxylic acid,

7-n-propyll()-oxothioxanthone-2-carboxylic acid, 7n-propyll U, l(l-dioxothioxanthone-Z-carboxylic acid, 7isopropyl-10-oxothioxanthone-Z-carboxylic acid, 7-isopropyl-1(J,l()-dioxothioxanthone-Z-carboxylic acid, and so forth, 7methoxy-1()-oxothioxanthone-2-carboxylic acid,

7-methoxyl O, 1 O-dioxothioxanthone-2-carboxylic acid,

7-ethoxylO-oxothioxanthone-Z-carboxylic acid,

7-ethoxy-l0,10-dioxothioxanthone-Z-carboxylic acid,

7-n-propoxyl O-oxothioxanthone-Z-earboxylic acid,

7-n-propoxyl O, l O-dioxothioxanthone-Z-carboxylie acid,

7-isopropoxyl ()-oxothioxanthone-2-carboxylic acid,

7-isopropoxyl 0, l O-dioxothioxanthone-2carboxylic acid, and so forth,

7-methylthi0-10-oxothioxanthone-2-carboxylic acid,

7-methylthi0-10,l O-dioxothioxanthone-2-carboxylie acid,

7-ethylthio-10-oxothioxanthone-2-carboxylic acid,

7-ethylthio-10,10-dioxothioxanthone-2carboxylic acid,

7-n-propylthiolO-oxothioxanthone-2-carboxylic acid,

7-n-propylthiol 0, l O-dioxothioxanthone-Z- carboxylic acid,

7-isopropylthi0- l -0xothioxanthone-Z-carboxylic acid,

7-isopropylthio-l0,10-dioxothioxanthone-2- carboxylic acid, and so forth,

7-acetyll O-oxothioxanthone-Z-carboxylie acid,

7-acetyll0, 1 O-dioxothioxanthone-2-carboxylic acid,

7-propionyll O-oxothioxanthone-Z-carboxylic acid,

7-propionyll O, l()-dioxothioxanthone-Z-carboxylic acid, and so forth,

7-cyclopropylearbonyllU-oxothioxanthone-2- carboxylic acid,

7-cyclopropylearbonyl-10,10-dioxothioxanthone-2- earboxylie acid.

7-cyelobutylcarbonyll O-oxothioxanthone-Z- carboxylic acid,

7-cyclobutylcarbonyl-lO,10-dioxothioxanthone-2- carboxylic acid, and so forth,

7-benzoyl-l()-oxothioxanthone-Z-carboxylic acid,

7-benzoyl-l0,10-dioxothioxanthone-Z-carboxylic acid, and so forth,

7-furoyll()-oxothioxanthonc-Z-earboxylic acid,

7-furoyl-10,l()-dioxothioxanthone-Z-carboxylic acid,

7-pyrroyll O-oxothioxanthone-2-carboxylic acid,

7-pyrroyl-l(),l()-dioxothioxanthone-2-carboxylic acid,

7-thenoyll ()-oxothioxanthone-Z-carboxylic acid,

7-thenoyll (l, l(l-dioxothioxanthone-Q-carboxylic acid, and so forth.

The hydroxy compounds can be prepared from the lower alkoxy compounds of Example 4 according to the following representative procedure.

EXAMPLE 6 A mixture of l 1 grams of7-(methoxy)-thioxanthone- Z-carboxylic acid in 100 ml. of concentrated aqueous hydrogen iodide and 100 ml. of acetic acid is refluxed for 4 hours, After this time, the mixture is cooled, diluted with water, and filtered. The precipitate is washed and dried to give 7-(hydroxy)-thioxanthonc-2- carboxylic acid. I

EXAMPLE 7 This example illustrates the manner by which the esters of the and 7-(hydroxyJ-thioxanthone-Z- carboxylic acids are prepared.

A mixture ofZ grams of 7-(hydroxy l-thioxanthone-Z- carboxylic acid in 8 ml. of pyridine and 4 ml. of acetyl chloride is heated at steam bath temperatures for 1 hour. The mixture is then poured into ice water and the solid which forms is collected by filtratitw 'washed with water and dried to yield 7-(acetoxy)-thioxanthone-2- carboxylic acid which is further purified through recrystallization from acetic acid.

In a similar manner, S-(acetoxy )-thioxanthonc-2- carboxylic acid is prepared Upon substitution of the appropriate alkanoyl chloride in the above procedures, the other 5- and 7-esters can be prepared, e.g.

S-(propionyloxy)-thi0xanthone-Z-earboxylic acid,

7-(propionyloxy)-thi0xanthone-2carboxylic acid,

5-(butyryloxy)-thioxanthone-2-earboxylie acid, 7-(butyryloxy)-thioxanthone-2-earboxylic acid,

S-(triehloroacetoxy)-thi0xanth0ne-2-earboxylic acid, 7-(trichloroacetoxy)-thioxanthone-2-carboxylic acid,

S-(trimethylacetoxy)-thioxanthone-Z-carboxylic acid, 7-(trimethylacetoxy)-thioxanthone-Z-carboxylic acid,

5-(heptanoyloxy)-thioxanthone-2-carboxylie acid,

7-(heptanoyloxy)-thioxanthone-Z-carboxylic acid,

5(pentanoyloxy)-thioxanthone-Z-earboxylic acid, 7-(pentanoyloxy)-thioxanthone-Z-carboxylic acid,

5-( Z-chloropropionyloxy )-thioxanthone-2- carboxylic acid,

7-( 2-chloropropionyloxy )-thioxanthone-2- carboxylic acid, and so forth.

EXAMPLE 8 A mixture of 3.9 grams of l,3-dicarbomethoxy-4- bromobenzene, 2.85 g. of p-(aeetyl)-thiophenol, 1.1 g. of cuprous oxide. and 25 ml. of tetramethylurea is heated to 165C and maintained thereat with stirring for 18 hours under a nitrogen atmosphere. After this time, the reaction mixture is diluted with water and extracted with ether. The extracts are dried and evaporated to give l,3-dicarbomethoxy-4(p-(acetyl)-thiophenyloxy)-benzene.

l,3-Dicarbomethoxy-4-( p-(acetyl )-thi0phenyloxy benzene (3.5 grams) is dissolved in 50 ml. of ethanol and the mixture treated with 15 mlv of 4% aqueous potassium hydroxide solution. The reaction mixture is refluxed for 30 minutes, concentrated under reduced pressure, and acidified with dilute hydrochloric acid. The solid collected upon filtration is washed with water and dried to give l,3-dicarboxy-4-(p-(acetyl)-thiophenyloxy)-benzene which is recrystallized from ethanokwater.

A. solution of 3.2 g. of 1,3-dicarboxy-4-(p-(acetyl)- thio henyloxyl-benzenc in 30 ml. of concentrated sulfuric acid is warmed to C. The mixture is then allowed to stand at room temperature for 16 hours after which time it is poured into ice water, filtered, washed and dried to give 7-(acetyl )-thioxanthone-Z-carboxylic acid which is recrystallized from tetrahydrofuran1ethanol. v

In a similar manner, the above described reactions can be conducted utilizing an alternate paeyl phenol starting material to give the corresponding 7(acyl)- thioxanthonc-lcarlmxylic acid products, cg.

7-( forniyl )-thioxanthonc-Z-carboxylic acid,

7-( propionyl)thioxanthone-Z-carboxylic acid,

7-( n-butyryl)-thioxanthone-2-carboxylic acid,

7-( isobutyryl )-thioxanthone-2-carboxylic acid,

7-(n-pentanoyl )thioxanthone-2-earboxylic acid,

7-(isopentanoyl )-thioxanthone-Z-carboxylic acid, 7-(sec-pentanoyl)-thioxanthone-Z-carboxylic acid, 7-(t-pentanoyl)-thioxanthone-2-carboxylic acid, 7-(hexanoyl) thioxanthone-2-carboxylic acid, 7-(heptanoyl)-thioxanth0ne2-carboxylic acid, 7-(octanoyl)-thioxanthone-2carboxylic acid,

7-( nonanoyl )-thioxanthone-2-carboxy1ic acid,

7-( cyclopropylcarbonyl )-thioxanthone-2-carboxylic acid,

7-( eyelobutylcarbonyl )-thioxanthone-Z-carboxylic acid, I

7-( cyclopentylearbonyl )-thioxanthone-2-carboxylic acid,

7-( cyelohexylcarbonyl )-thioxanthone-2-carboxylie acid,

7-(haloacetyl)-thioxanthone-2-carboxylic acid,

7-( benzoyl)-thioxanthone-Z-carboxylic acid,

7-(substituted benzoyl)-thioxanthone-Z-carboxylic acid,

7-( heterocyeliccarbonyl )-thioxanthone-2-carboxylic acid, and the 10oxo and 10,10-dioxo derivatives thereof.

The procedure of Example 8 is repeated using the appropriate o-(acyl)-thiophenol starting compounds to prepare the corresponding substituted thioxanthone2-carboxylic acid, to wit, 5-(formyl)- thioxanthone-Z-carboxylic acid, S-(acetyl thioxanthone-Z-carboxylic acid, S-(propionyl thioxanthone-Z-carboxylic acid, 5-(n-butyry1)- thioxanthone-Z-carboxylie acid, 5-( isobutyryl thioxanthone-Z-carboxylic acid, and so forth.

EXAMPLE 9 To a solution of 25 grams of thioxanthone-2- carboxylic acid in 200 ml. of triethylene glycol are added 18 g. of potassium hydroxide and 12.1 g. of95% hydrazine. The resultant mixture is heated to reflux 155C) and maintained thereat for one hour. The distillate is removed and the temperature is held at a temperature of about 200C for 2 hours. The mixture is then cooled to 68C and 200 ml. of water is added and the resultant solution poured into 1 10 ml. ofwater containing 60 ml. of concentrated hydrochloric acid. The resultant mixture is heated to 90C, cooled to room temperature and filtered to give thioxanthene-Z- carboxylic acid.

Twenty-six grams of thioxanthene-2-carboxylic acid is added to 400 ml. of absolute methanol. To the resultant solution are added 18 ml. of concentrated sulfuric acid and the mixture is then heated at reflux for about 2 hours. The mixture is then cooled to 40C and suffl cient water is added to bring the total volume to 1400 ml. The resultant mixture is then filtered to give methyl thioxantheneQ-carboxylate.

A mixture of 13.0 g. of methyl thioxanthene-Z- carboxylate in 200 ml. of dichloroethane is cooled to 5C and to the cooled solution are added 4.95 ml. of acetyl chloride and then 17.0 g. of aluminum trichloride. The resultant solution is stirred at room temperature for 1.75 hours. After this time, the solution is poured into a mixture of 300 g. ofice, 700 ml. of water, and 20 ml. of concentrated hydrochloric acid. The mixture is then extracted with three 500 ml. portions of methylene chloride. The combined extracts are washed with 10% aqueous potassium hydroxide solution and the washed solution evaporated to give methyl 7- (acetyl )-thioxanthene-2-carboxylate.

To a solution of 1.42 g. of methyl 7-(aeetyl) thioxanthene-2carboxylate in 120 ml. of benzene are added 12.5 g. of manganese dioxide. The resultant mixture is stirred at room temperature for 16 hours after which time the mixture is filtered and stripped of solvent to give methyl 7-(acetyl)-thioxanthone-2- carboxylate which is recrystallized from methanol (displacement from methylene chloride solution).

A solution of 2 g. of methyl 7-(acetyl)-thioxanthone- Z-carboxylate in 200 ml. of 10% aqueous, 10% potassium hydroxide in methanol is heated at reflux under a nitrogen atmosphere for minutes. After this time, 20 ml. of water are added and the resultant mixture heated at reflux for 35 minutes. Water (300 ml.) is then added and the resultant mixture acidlified and filtered to give 7-(acetyl )-thioxanthone-2carlboxylic acid.

l0-Oxo-7-( acetyl )-thioxanthone-Z-carboxylic acid and l0,10-dioxo-7-(acetyl)-th.ioxanthone2-carboxylic acid are also thus prepared.

EXAMPLE 10 The procedure of Example 9 is repeated employing, in the procedure of the third paragraph thereof, the acyl chlorides (prepared from the corresponding acids upon treatment with thionyl chloride or oxalyl chloride) listed in Column A below to prepare the corresponding acid products listed in Column B below, through their respective methyl esters.

Column A ('oltnnn B propionyl chloride 7-( prupionyl )-thioxanthonc2- 7-( t-pentanoyl )-thioxanthone-2- carhoxylic acid t-pcntanoyl chloride nhexano \'l chloride 7-( n-hexanoyl J-thioxanthonedcarhox lic acid n-hcptanoyl chloride 7-( n-oclunoyl )-thioxanthone-2-- carboxylic acid n-octnnoyl chloride 7-( rHionanoyl )-thioxanthonc l earboxylic acid n-nonanoyl chloride 7-( cycloprropylcarbonyl J-thio cyelopropy lcarbonyl xanthone-Z-carhoxylic acid chloride cyclt)hutylcarhonyl chloride 7-( cyclohutylearbonyl J-thioxanthone-Z-carhox ylie acid cyclopentylcarlmnyl 7-( cyclopentylcarbony| )-thiochloride xanthone-2-carboxylic acid cyelohexylcarbonyl 7-( cyelohexylcarbonyl )-thiochloride xanthonc-Z-carboxylic acid -Continued Column A Column B BENZOY L CHLORIDE 7-( benzoyl l-thioxanthone2 7-( p'mcthylhcnzoyl )-thioxanthonc Z-carhoxylic acid p-mcthylhcmoyl chloride p-methoxybcnzoyl chloride 7-( pmethox benxoyl l-thioxanthone- Z'carhoxyIic acid 7-( pthiomethoxybenzoyl l-thio- Xanthone-2carboxylic acid pthiomethoxybenzoyl chloride furoyl chloride 7*( furoyl )-thioxanthonc-Z- carboxylic acid 7-( pyrroyl J-thioxanthonc-Z- carboxylic acid pyrroyl chloride thcnoyl chloride 7-thenoyl )-thioxanthonc-2- carboxylic acid 7-( pyridylcarhonyl )-thioxanthonelcarhox; lic acid pyridylcarbonyl chloride 7-( imidalolylcarbonyl )-thioxanthone-2-carboxylic acid imidavolylcarbimy] chloride EXAMPLE 1 l A mixture of 1.077 grams of methyl 7-(acetyl)- thioxanthone-Z-carboxylate, 200 mg. of sodium horohydride and 150 ml. of tetrahydrofuran is stirred for 2.5 hours at room temperature. The reaction is monitored by tlc. After this period of time, a 5% aqueous acetic acid solution is added to the reaction mixture dropwise to neutrality and the resultant solution evaporated under vacuum and crystallized by the addition of ethanol and hot water. The precipitate is filtered off. washed and dried to give methyl 7-( l-hydroxyethyl)- thioxanthone-2-carboxylate.

A mixture of 860 mg. of methyl 7-( l-hydroxyethyhthioxanthone-2-carboxylate, 60 ml. of ethanol and 2 ml. of 2N sodium hydroxide is refluxed for minutes. The resultant mixture is cooled. acidified and the precipitate is filtered off, washed, and dried to give 7-( lhydroxyethyl )-thioxanthone-Z-carboxylic acid.

l()-Oxo-7-( l-hydroxyethyl )-thioxanthone-2- carboxylic acid and l(),l()-dioxo-7-( l-hydroxyethyl)- thioxanthone-Z-carboxylie acid are also thus prepared.

The foregoing procedures are practiced upon the other 7-acyl methyl esters prepared as described in Example l() to give the following products, through their respective methyl esters:

7( l-hydroxy-n-propyl )-thioxanthone-Z-carboxylic acid,

7-( 1-hydroxy-n-butyl)-thioxanthone2-carboxylic acid.

7-( l-hydroxyisobutyl )-thioxanthone-Z-carboxylic acid,

7-( l-hydroxy-n-pentyl )-thioxanthone-2-carboxylic acid,

7-( l-hydroxy-isopentyl )thioxanthone-2-carboxylic acid,

7-( l-hydroxy-sec-pentyl )-thioxanthone-2-carboxylic acid,

7-( l-hydroxy-t-pentyl )-thioxanthone-2-carboxylic acid,

7-( l-hydroxy-n-hexyl )-thioxanthone-2-carboxylic acid,

7-( l-hydroxy-n-heptyl)-thioxanthone2-carboxylic acid,

7-( l-hydroxy-n-octyl )-thi0xanthone-Z-carboxylic acid,

7-( l-hydr0xy-n-nonyl)-thioxanthone-2-carboxylic acid,

7-( (cyclopropyl hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-( (cyclobutyl )hydroxymethyl )-thioxanth0ne-2- carboxylic acid,

7-( (cyclopentyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-( (cyclohexyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-(hydroxymethyl)-thioxanthone-2-carboxylic acid,

7-( phenyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-( p-chlorophenyl )hydroxymethyl )-thioxanth0ne- Z-carboxylic acid,

7-((p-methylphenyl)hydroxymethyl)-thioxanth0ne- 2-carboxylic acid,

7-( p-methoxyphenyl )hydroxymethyl thioxanthone-Z-carboxylic acid,

7-( p-thiomethoxyphenyl )hydroxymethyl thioxanthone-2-carboxylic acid,

7-( furyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-( pyrryl )hydroxymethyl )-thioxanthone-2- carboxylic acid.

7-( thienyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7-( pyridyl )hydroxymethyl )-thioxanthone-2- carboxylic acid,

7( imidazolyl )hydroxymethyl )-thioxanth0ne-2- carboxylic acid,

7-( (oxazolyl )hydroxymethyl )-thioxanthone-2- carboxylic acid, and the lO-oxo and 10,10-di0xo derivatives thereof.

EXAMPLE 12 A solution of 4.1 grams of methyl 7-(acetyl)- thioxanthone-Z-carboxylate in l20 ml. of tetrahydrofuran is stirred at 0C and 6.8 ml. of 3M mcthylmagncsium bromide solution in ether are added dropwise. After stirring at 0C for 30 minutes, the reaction mixture is left to warm up to room temperature. A saturated ammonium chloride solution ml.) is then added and the mixture is concentrated in vacuo. Extraction with ethyl acetate followed by evaporation yields methyl 7-( l-hydroxyl -methylethyl thioxanthone-2-carboxylate.

The foregoing procedure is practiced upon the other 7-acyl methyl esters prepared as described in Example it) to give the following products, through their respective methyl esters:

7-( l-hydroxyl -methyl-n-propyl )-thioxanthone-2- carboxylate acid,

7-( l-hydroxy- 1 -methyl-n-butyl )-thioxanthone-2- carboxylic acid, 

1. A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING FORMULAS:
 2. A compound according to claim 1 of formula (A).
 3. A compound according to claim 1 of formula (B).
 4. A compound according to claim 1 of formula (C).
 5. A compound according to claim 4 wherein R is the group
 6. A compound according to claim 4 wherein R is the group
 7. A compound according to claim 4 wherein R Is the group
 8. A compound according to claim 4 wherein R is the group
 9. A compound according to claim 1 of formula (D).
 10. The compound according to claim 1 which is 7-(1-hydroxyethyl)-thioxanthone-2-carboxylic acid.
 11. The compound according to claim 1 which is 7-(acetyl)-thioxanthone-2-carboxylic acid.
 12. The compound according to claim 1 which is 7-(methylsulfinyl)-thioxanthone-2-carboxylic acid.
 13. The compound according to claim 1 which is 7-(methylsulfonyl)-thioxanthone-2-carboxylic acid.
 14. The sodium salts of the compounds of claim
 1. 15. A compound selected from the group consisting of: 5-isopropyl-7-(acetyl)-thioxanthone-2-carboxylic acid, 5-isopropoxy-7-(acetyl)-thioxanthone-2-carboxylic acid, 5-isopropyl-7-(methylsulfinyl)-thioxanthone-2-carboxylic acid, 5-isopropoxy-7-(methylsulfinyl)-thioxanthone-2-carboxylic acid, 5-acetyl-7-(isopropyl)-thioxanthone-2-carboxylic acid, 5-acetyl-7-(isopropoxy)-thioxanthone-2-carboxylic acid, 5-methylsulfinyl-7-(isopropyl)-thioxanthone-2-carboxylic acid, and 5-methylsulfinyl-7-(isopropoxy)-thioxanthone-2-carboxylic acid.
 16. The compound according to claim 15 which is 5-isopropyl-7-(acetyl)-thioxanthone-2-carboxylic acid.
 17. The compound according to claim 15 which is 5-isopropoxy-7-(acetyl)-thioxanthone-2-carboxylic acid.
 18. The compound according to claim 15 which is 5-isopropyl-7-(methylsulfinyl)-thioxanthone-2-carboxylic acid.
 19. The compound according to claim 15 which is 5-isopropoxy-7-(methylsulfinyl)-thioxanthone-2-carboxylic acid.
 20. The compound according to claim 15 which is 5-acetyl-7-(isopropyl)-thioxanthone-2-carboxylic acid.
 21. The compound according to claim 15 which is 5-acetyl-7-(isopropoxy)-thioxanthone-2-carboxylic acid.
 22. The compound according to claim 15 which is 5-methylsulfinyl-7-(isopropyl)-thioxanthone-2-carboxylic acid.
 23. The compound according to claim 15 which is 5-methylsulfinyl-7-(isopropoxy)-thioxanthone-2-carboxylic acid. 